The “this guy or that guy” debate is essential to any hot stove baseball discussion.

We thought we’d nose our way into that conversation with a series of “would you rather have” pieces comparing the merits — and risks — of players on the free-agent market. You won’t see a Bryce-or-Manny debate here, though, because Harper and Machado play different positions (obviously).

Our first entry looks at two outstanding lefty starters, two oft-injured outfielders and the top two hot corner guys on the market.

Patrick Corbin or Dallas Keuchel

The need-to-knows: Corbin and Keuchel are the top two left-handed starters on the market. Keuchel has the better track record, but Corbin had the better 2018 season. Corbin will be 29 on Opening Day; Keuchel will be 31. Both declined qualifying offers, which means the team that sign them will forfeit a draft pick.

The case for Corbin: The lefty was an All-Star in 2013, but he missed the 2014 season (Tommy John surgery), made only 16 starts in his 2015 return and struggles landed him in the bullpen late in the 2016 campaign. He was solid in 2017 — 189 2/3 innings, 4.03 ERA/4.08 FIP, but with a 1.418 WHIP — but that was just a warm-up for what was in store for 2018.

Corbin added a slow curve to his repertoire for 2018, and everything else fell into place. His strikeouts per nine innings jumped to 11.1, up from a career average of 7.9, and his K/9 ratio shot to 5.13, up from a career 2.92. Not surprisingly, he posted career bests in ERA (3.15) and FIP (2.47). I asked him at the All-Star media day what he attributed his success to.

“Adding another breaking ball in the low 70s, backing that up with my harder slider, and changeup as well,” he told Sporting News. “Just keeping hitters off-balance, working ahead in the count, locating my fastball a lot better and being able to throw that pitch where I want to. It was never a plan to strike out more guys, but it just kind of worked out. I’m trying to get ahead of them, and when you get two strikes, you try to put them away or make a really tough pitch.”

Will Corbin repeat his 2018 performance? That’s the question teams have to weigh this offseason, because a 29-year-old with a 2.45 FIP and 11.1 K/9 is worth significantly more than a 29-year-old with a 4.08 FIP and 8.4 K/9. You still want the second guy, but the first one is worth a premium contract.

The case for Keuchel: There are a couple of ways to look at Keuchel’s 2018 season. On one hand, several stats jumped in the wrong way: ERA (from 2.90 in 2017 to 3.74), WHIP (1.119 to 1.314), H/9 (7.2 to 9.3) and K/9 (7.7 to 6.7). On the other hand, the lefty’s FIP actually dropped (3.79 to 3.69), his K/9 ratio was nearly identical (2.66 to 2.64) and his percentages of home runs and walks allowed both went in the right direction.

His days as a Cy Young contender — he won the AL award in 2015 — might be in the past, but he has plenty of productive days ahead of him. His velocities stayed consistent through 2018 compared to career norms, and his four-seam velocity in September was the highest of the season, following a pattern of getting stronger that Keuchel’s had the past several years.

His October track record is strong, too. In 10 career playoff games (nine starts), Keuchel has a 3.31 ERA, including two solid five-inning starts in the 2018 postseason. He would make a solid middle-of-the-rotation guy for a WS contender, or a great veteran leader addition near the top of the rotation for a team looking to take a jump into contention (think, loosely, about the Cubs signing Jon Lester before the 2015 season).

Verdict: This new version of Corbin is worth the higher price, especially when factoring in age.

Michael Brantley or A.J. Pollock

The need-to-knows: Brantley and Pollock are All-Star caliber outfielders who have had issues staying healthy. Pollock turns 31 in a couple of weeks, and Brantley turns 32 in mid-May. Pollock turned down Arizona’s qualifying offer, so signing him comes with draft-pick compensation. Brantley was not given a QO (a bit surprising) by Cleveland.

The case for Brantley: First, the injury issues. The left-handed hitter with the smooth swing finished third in the 2014 AL MVP race and followed that up with another solid season in 2015 (AL-best 45 doubles, 15 homers, 15 stolen bases), despite injuries that limited him to 137 games. But he played just 11 games in 2016 and 90 in 2017, knocked out by frustrating shoulder and ankle issues that clouded his future.

Brantley was healthy, finally, for most of the 2018 season. He played 143 games, made the All-Star team for the third time and posted a 3.6 bWAR, .309 average, 123 OPS+, 36 doubles, 17 homers, 12 stolen bases and a .364 on-base percentage. In other words, exactly what you’d expect from Brantley when healthy. It’s worth noting, too, that Brantley is the kind of future-coach-veteran who makes a positive impact in the clubhouse even when he’s on the DL.

The case for Pollock: His 2015 season was underrated by MVP voters; he finished 15th despite a 7.2 bWAR, 20 homers, 39 stolen bases, 111 runs scored, .315 average and .865 OPS. Unfortunately, Pollock fractured his elbow on a slide into home in an exhibition game two days before the start of the 2016 season and missed all but 11 games. In 2017, he played 112 games, missing a large chunk of time with a Grady 1 groin strain. In 2018, he played 113 games, with most of the games missed attributed to a fractured thumb.

His per-162 games projections for the past two seasons check in at 26 homers and 24 stolen bases. But health is a real the thing teams have to consider. He’s been in the majors for six full seasons, and he’s played more than 113 games just twice. On the other hand, though, it’s not like he’s suffered from chronic-type issues, like back or shoulder trouble. His issues have been largely broken bones.

Verdict: Teams will roll the injury dice to sign either guy. Pollock has the higher upside, but for a team that is loathe to part with any draft pick, Brantley might be the better bet.

Josh Donaldson or Mike Moustakas

The need-to-knows: Donaldson and Moustakas are the top two free-agent third basemen on the market; Donaldson turns 33 in early December, and Moustakas turned 30 in September. Neither player was eligible for a QO, so neither is attached to draft-pick compensation.

The case for Donaldson: From 2013-16, Donaldson posted an average 7.8 bWAR, finished in the top eight of the AL MVP voting four times — he won the 2015 award — sported a 144 OPS+ for Oakland and Toronto and averaged 157 games a season. And despite missing six weeks with a calf injury in 2017, he still popped 33 homers and had a 4.8 bWAR in 113 games. He was, without a doubt, one of MLB’s best players, not only because of his bat but because of his defense at the hot corner.

The 2018 season, though, was an exercise in frustration. After a short disabled list stint for a shoulder issue, Donaldson spent more than three months on the DL with calf issues, including a fair number of setbacks from the original timeline. The Blue Jays traded him to Cleveland, and he finally returned to action on Sept. 11 wearing his new uniform. Donaldson looked good at the plate in his small sample size, popping three homers and posting a .920 OPS in 16 games.

The question is what type of contract Donaldson wants, and what type of contract teams are willing to give him. Does he want a one-year deal, betting that he’ll prove himself healthy in 2018 and test the market again next offseason at 34 years old, after a vintage Donaldson season? Or does he realize that players that age aren’t landing five- or six-year deals anymore and try to maximize what he can get this offseason? It’s not unreasonable to think enough teams are intoxicated by his talents that he could land a multiple-year deal packed with incentives (and/or options).

The case for Moustakas: The strangeness of last winter’s offseason impacted Moustakas as much (or more) than anyone. Coming off a 38-homer season with the Royals, he turned down the team’s qualifying offer (a no-brainer move) and waited for teams to woo him with lucrative long-term contract offers. That didn’t happen, of course, and he wound up taking a deal to return to K.C. in spring training. Unlike some of his fellow late signees, Moustakas had a solid 2018 season, posting 28 homers, 95 RBIs and a 2.5 bWAR split between the Royals and Brewers (he had eight homers and 33 RBIs in 54 games with Milwaukee).

This year, with no draft-pick compensation attached, Moustakas figures to have more options. He is what he is — a solid defensive third baseman with good power (66 homers the past two years) and a World Series ring on his resume, but a low on-base percentage (.315 the past two years). He’s not an upgrade for every team, but he is for enough teams that he’ll get multiple-year offers.

Verdict: Donaldson’s worth the risk, as long as the contract doesn't have insane money/years guarantees.